1. Field of the Invention
The present invention relates to a position adjuster and a position adjusting method of an optical modulator for adjusting relative position of optical modulators used for producing a projector, the projector having a color separating optical system for separating a light beam irradiated by a light source into a plurality of color lights, a plurality of optical modulators for modulating the respective color lights separated by the color separating optical system in accordance with image information and a color combining optical system for combining the light beam modulated by the respective optical modulators.
2. Description of Related Art
Conventionally, a projector having a plurality of optical modulators (liquid crystal panels) for modulating a plurality of color lights respectively in accordance with image information, a color combining optical system (cross dichroic prism) for combining the color lights modulated by the respective optical modulators, and a projection optical system (projection lens) for enlarging and projecting the light beam combined by the color combining optical system to form a projected image has been used.
So-called three-plate projector is known as such projector, in which a light beam irradiated by a light source is separated into three color lights of red, green and blue by a dichroic mirror, the separated light beam is modulated for each color light in accordance with image information and the modulated light beam is combined by the cross dichroic prism to enlarge and project the color image through a projection lens.
In order to obtain a vivid projection image by the projector, it is necessary to prevent picture element deviation among the respective liquid crystal panels and distance gap from the projection lens, so that focus and alignment between the respective liquid crystal panels have to be adjusted with high accuracy in producing the projector.
The focus adjustment refers to adjustment for accurately locating the respective liquid crystal panels at a back focus position of the projection lens and the alignment adjustment refers to adjustment for coinciding the picture elements of the respective liquid crystal panels, which also apply in the following description.
The focus and alignment adjustment of the liquid crystal panel has been conventionally conducted by adjusting an optical unit including three liquid crystal panels, a cross dichroic prism and a projection lens, where (1) a light beam is irradiated on an image formation area of the respective liquid crystal panels, (2) the projected image passing through the cross dichroic prism and the projection lens is displayed on a screen, (3) the reflected light of the image projected on the screen is taken by a beam sensor such as a CCD camera fixed at a predetermined position and (4) the relative position of the respective liquid crystal panels is adjusted by a position adjusting mechanism while checking the focus, picture element position etc. of the respective liquid crystal panels detected by the CCD camera. In other words, the position of the respective liquid crystal panels has been adjusted based on the position of the image projected on the screen.
Conventionally, in order to project an image on a screen, an arrangement where an optical unit and a screen are disposed along an optical axis of a projection lens and the projected light from the optical unit is directly projected on the screen (conventional example 1) and another arrangement having a reflector for reflecting a light of a light source passing through a liquid crystal panel and a prism along a first direction into a second direction different from the first direction and a screen onto which the light of the light source reflected by the reflector along the second direction is projected (Japanese Patent Laid-Open Publication No. 2000-147654; conventional example 2) have been proposed.
However, according to the conventional example 1, since the image is projected on the screen and the optical unit and the screen are linearly disposed along the optical axis of the projection lens, large-size screen is necessary, thereby increasing the whole size of the device.
In the conventional example 2, though the size of the screen can be reduced-as compared to the conventional example 1 by reflecting the light projected by the projection lens with the reflector through a mirror, there is certain limit in size reduction of the whole device because of the use of the screen.
Accordingly, since the screen is necessary in both arrangements, large-scale device is necessary and solution thereof has been strongly desired.